This section provides background information related to the present disclosure which is not necessarily prior art. With the advent of legislation in California (AB 1953), lead in brass components for potable water systems was mandated to contain less than 0.25% lead by weighted average starting Jan. 1, 2010. Since establishment of this legislation, additional states including Vermont, New Hampshire, Maryland and Louisiana have followed suit. National legislation has also recently been passed requiring all fifty states to supply lead free brass (less than 0.25% lead) for potable water applications by Jan. 1, 2014.
The removal of lead from brass significantly affects machinability of the materials. To overcome these problems, adjustments to the microstructure have been made. Unfortunately, the change in microstructure leads to increased dezincification. Dezincification is generally defined as a selective process by which zinc is removed from the alloy leaving behind a porous, copper-rich structure that has little mechanical strength.
Lead free brass further presents some significant challenges for the brass industry. Lead in brass acts as a chip breaker for the metal during machining. Additionally, the lead provides lubrication for the cutting tools. The absence or reduction of lead in brass for these functions reduces the machinability of brass. This, in turn, reduces productivity which results in driving up the cost of the finished parts. Existing Unified Numbering System 2000 series lead free brass alloys exhibit conventional machinability ratings in the range of 20% to 40% machinability compared to its leaded brass alloys counterparts.
Optionally, dezincification inhibition of the alpha phase in brass can be accomplished with certain corrosion inhibitors. Since duplex brasses contain a large amount of alpha phase, it is essential that an inhibiting agent be present in duplex brasses to assist with dezincification protection. Of the known inhibitors, arsenic is the most effective in improving dezincification resistance. There are a number of alloys that employ arsenic as an inhibitor. Although commonly used in Australia and Europe, there is a negative perception of arsenic as an inhibitor in potable water systems in the United States. Antimony is another effective inhibitor, but can result in processing issues such as cracking. These corrosion inhibitors however do not assist in reducing dezincification in the beta phase of duplex brasses. There is therefore a need for a brass for water systems which meets the new regulatory environment, is machinable, and does not suffer from dezincification.